Apparatus for increasing blower air pressure in scavenging diesel engines



United States Patent [72] inventors Thomas H. Boyce, Jr.;

Robert W. Mitchell, Houston, Texas [2]] Appl. No. 790,330 [22] Filed Jan. 10,1969 [45] Patented Nov. 17, 1970 [73] Assignee Stewart & Stevenson Services, Inc. Houston, Texas a corporation of Texas [54] APPARATUS FOR INCREASING BLOWER AIR PRESSURE IN SCAVENGING DIESEL ENGINES 3 Claims, 2 Drawing Figs.

Primary Examiner-Wendell E. Burns Attorneys-James F. Weller, Jefferson D. Giller,

William A. Stout, Paul L. De Verter, 11, Dudley R. Dobie, Jr. and Henry W. Hope ABSTRACT: An apparatus for allowing operation at low speeds of a two-cycle uniflow scavenged type compression 1gnition diesel engine by providing a speed step up for increasing the blower speed. A shaft extension connected to the blower rotor gear connected to speed increasing means for increasing the blower speed. A first hollow shaft gear having a hollow shaft coupling connected to the blower drive gear and meshing with a second smaller gear to provide a first stage step up speed with a third gear larger than the second gear connected to the shaft of the second gear and a fourth gear smaller and meshing with the third gear to provide the second stage speed up with a blower drive shaft connected to the fourth gear and through the hollow first gear shaft and coupling to the blower rotor gear.

Patented Nov. 17, 1910 v 3,540,421

ATTORA/EVJ 7720/7700 Boyce, cf

APPARATUS FOR INCREASING BLOWER AIR PRESSURE IN SCAVENGING DIESEL ENGINES BACKGROUND OF THE INVENTION Diesel engines such as the V-type series 71 of the Detroit Diesel Engine Division of General Motors are normally designed for operations at rotative speeds in excess of 1,200 r.p.m. While it is desirable in some applications to operate such an engine at slower than the minimum designed speed, operation at such lower speeds can cause excess carboning, sludging and horse power loss. In addition, the inherent design of theseparticular engines is such that their internal configuration and dimensions do not allow changing the gear ratio of the blower sufficiently to overcome the low operating speed problem.

SUMMARY OF THE INVENTION The present invention is directed to providing an increase in the scavenging blower speed to increase air manifold pressure.

The invention provides for blower speed increase by providing a blower rotor gear extension connected to a speed step-up means driven from the blower drive gear.

The present invention is further directed to providing an apparatus for increasing the scavenging air pressure in the air manifold at speeds below 1,200 rpm. in a twocycle unitlow scavenge type V'compression ingnition diesel engine having a scavenging blower by providing a first hollow shaft gear having a hollow shaft coupling connected to the blower drive gear with a second smaller gear connecting with the first gear and a third gear larger than the second gear connected to the shaft of the second gear with a fourth gear smaller than the third gear meshing with the third gear, and connecting the blower drive shaft to the fourth gear and passing it through the hollow shaft firsrgear and coupling and connecting it to the blower rotor gear to provide a two stage speedup for the blower.

The invention further includes providing the fourth gear with a hollow shaft whereby the blower drive shaft passes through the fourth gear hollow shaft and is connected to the fourth gear on the side remote from the blower rotor gear for balancing the forces on the shaft and wherein a housing is provided surrounding the gears and connected to the diesel engine lube oil system for providing lubrication.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic elevational view ofa two-cycle blower scavenged diesel engine, and

FIG. 2 is an enlarged cross-sectional view of the blower speed up gear box of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, particularly to FIG. 1, the reference numeral generally indicates a conventional twocycle diesel engine having a blower 12 which blows air into an air box or manifold 14 and in turn into the cylinders such as 16 for expelling exhaust gases therefrom and to supply the cylinders with fresh air for combustion. The cylinder wall contains a row of ports 18 which are above the piston 20 when the piston is at the bottom of its stroke. These ports 18 admit the air from the blower air box 14 into the cylinders 16 as soon as the piston 20 uncovers the ports 18. The unidirectional flow of air towards the exhaust valves 22 produces a scavenging effect leaving the cylinders 16 free of clean air when the pistons 20 again cover the inlet ports 18. As each piston 20 continues its upward stroke, the exhaust valves 22 close, the air is subject to compression so that as the fuel is sprayed into the cylinders 16 the fuel is ignited and the resulting pressure forces the piston 20 downwardly on the power stroke. The exhaust valves 22 are again opened when the piston 20 is down below the inlet ports 18 allowing the burned gases to escape into the exhaust manifold 24. Thereafter, the downward moving piston uncovers the inlet ports 18 and the cylinders are again swept with clean scavenging air and the cycle continued.

However, the inherent design of the V-type diesel engine designed for operation in excess of 1,200 r.p.m. is that when they are operated at speeds of lower than 1,200 rpm. the scavenging air pressure in the air box 14 on the outlet side of the blower 12 is so reduced as to impair proper scavenging of the exhaust gas and isinsufficient to provide enough combustion air to maintain clean and satisfactory operation over sustained periods under some operating conditions. Because of the insufficient air volume and pressure in the air box 14, with resulting poor combustion and insufficient differential pressure between the air box 14 and the inside of the cylinder adjacent the ports 18, carbon particles and contaminated air can be emitted into the air box 14 ofthe engine from the cylinders 16. That is, the pressure and volume of air in the air box 14 at low rotative engine speeds can be lower than the pressure in the cylinders 16 at the ports 18 slightly after the ports are opened on the downward power stroke of the engine. This condition tends to carbon up the intake ports 18, fill the air box 14 with carbon formation and the lack of sufficient clean air in the air box 14 further impairs clean combustion thereby aggravating the carboning conditions and shortening the intervals between necessary repair and maintenance as well as reducing horse power output.

Therefore, one way to overcome these problems is to increase the blower speed at lower rotative engine speeds, but the internal configuration and dimensions of the engine are such that the rpm. of the blower 12 cannot be increased by changing the gear ratio sufficiently to overcome the low pressure conditions.

Therefore, the present invention is directed to providing any suitable speedup means such as gear, chains, belts and pulleys connected between the blower drive gear and the blower rotor gear to step up the rotor speed.

Referring now to FIG. 2, a portion of the engine housing is indicated by the numeral 26 which encloses the blower drive gear 28 and the blower rotor gear 30 which turns the blower 12. One type of speed increaser of the present invention is generally indicated by the reference numeral 32 and includes a housing 34 which is externally connected to the engine housing 30. A two stage gear step-up train may be provided which includes a first gear 36 having a hollow shaft 38 and a coupling 40 also having a hollow shaft 42. The coupling 40 is connected to the blower drive gear 28 such as by 44. The first gear 36 is suitably supported on bearings 46 and 48.

A second gear 50 being smaller in diameter and has fewer teeth than the first gear 36 and is provided meshing with the first gear 36 to provide a first stage step-up speed. The second gear 50 is connected by a shaft 52 to a third gear 54. Gear 54 is larger than the second gear and has more teeth and is in turn connected to the fourth gear 56 having a hollow shaft 57, which gear 46 is a smaller gear thereby providing the second stage ofa step-up speed. Shaft 52 of gears 50 and 54 is suitably supported from bearings 58 and 60.

A blower drive shaft 62 is provided connected to the fourth gear 56 by a coupling 64 and extends through the hollow shaft 57'. of the fourth gear 56, through the hollow shaft 58 of the first gear 36 and through the hollow shaft 42 of the coupling 40 and is connected to the blower rotor gear 30. Thus, the manner of connections insures no unbalanced loads will be exerted on shaft 62 and the gear train.

It is noted that the speed increaser 32 makes no internal modifications to the engine and'does not impose any additional settings on the engine gear train or require any modifications to the existing engine. Since the housing 34 is externally connected to the engine housing 26 the gear box will derive its lubrication from the engine lube oil system. The speed increaser 32 requires no special tools or skills and any time that it becomes desirable to convert the engine back to standard speed operation, the speed increaser 32 may be simply removed.

In operation, the blower drive gear 28 rotates from the engine conventionally and in turn rotates coupling 40, first gear 36 which in turn drives second gear 50 at a faster speed and third gear 54 is driven through shaft 52 by a second gear 50 and in turn provides a second stage step-up speed by driving fourth gear 56. Fourth gear 56 is connected to coupling 64 and rotates the blower drive shaft 62 which is connected to and in turn drives blower rotor gear which drives the blower 12 to provide an increased air pressure in the manifold or air box 14 to overcome the problems previously mentioned.

The present invention, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein. While a presently preferred embodiment of the invention has been given for the purpose of disclosure, numerous changes in the detail of construction and arrangement of parts may be made which will readily suggest themselves to those skilled in the art and which are encompassed within the spirit of the invention and the scope of the appended claims We claim:

1. An apparatus for providing increased scavenging air pressure in the air manifold at speeds below L200 rpm. in a twocycle uniflow scavenged type V-Compression ignition diesel engine having a scavenging blower having a blower drive gear driving the blower rotor gear by increasing the blower speed comprising:

a first hollow shaft gear having a hollow shaft coupling connected to the side of the blower drive gear;

a second gear smaller than said first gear and meshing with the first gear providing a first stage step-up speed;

a third gear larger than the second gear connected to the second gear by an axial shaft;

a fourth gear smaller than the third gear and meshing with the third gear providing a second stage step-up speed, the axis of the fourth gear aligned with the axis of the first gear and hollow shaft coupling;

a blower drive shaft connected to the fourth gear and passing through the hollow shaft first gear and coupling and connected to the blower rotor gear; and

the fourth gear having a hollow shaft and the blower drive shaft passing through said fourth gear hollow shaft and connected to the fourth gear on the side remote from the blower rotor gear.

2 The apparatus of claim 1 wherein said first, second, third and fourth gears are positioned on the side of the drive gear remote from the rotor gear for converting said engine to a low speed operation.

3. An apparatus for providing operation at low speeds of a two-cycle uniflow scavenged type compression ignition diesel engine having a scavenging blower having a blower drive gear for driving the blower rotor gear, said drive gear and said rotor gear being mounted coaxially and side to side inside the engine housing, by increasing the scavenging air pressure in the air manifold of said engine by increasing the blower speed comprising:

a first hollow shaft gear having a hollow shaft coupling connected to the side of the blower drive gear;

a second gear smaller than said first gear and meshing with the first gear providing a first stage step-up speed;

a third gear larger than the second gear connected to the second gear by an axial shaft;

a fourth gear smaller than the third gear and meshing with the third gear providing a second stage step-up speed, the axis of the fourth gear aligned with the axis of the first gear, hollow shaft coupling and drive and rotor gear;

a blower drive shaft connected to the fourth gear and passing through the hollow shaft first gear and coupling and drive gear and connected to the blower rotor gear; and

said first, second, third and fourth gears are positioned on the side of the drive gear remote from the rotor gear for converting said engine to a low speed operation. 

